Technical Field
The present disclosure relates to an optical inspection system, and more particularly, to a three-dimensional measurement system.
Description of Related Art
In general, methods for measuring the three-dimensional shape of a DUT (device under test) can be divided into contact type methods and non-contact type methods. Non-contact type methods typically involve projecting a laser spot, a laser beam, or a structured (e.g., striped) light onto a DUT and then respectively scanning point-by-point, line-by-line, or the deformed stripes. Based on the triangular relationship among the light source, the DUT, and the imaging position, the height values of the three-dimensional shape of the DUT can be calculated.
FIG. 7 is a schematic diagram illustrating a conventional optical inspection system 7. As shown in FIG. 7, the optical inspection system 7 has two light sources 70 and a camera 72. The light sources 70 are respectively located at two sides of a DUT 2 and emit light toward the DUT 2. The camera 72 is located right over the DUT 2 for receiving light reflected from the DUT 2 to thereby generate corresponding images of the DUT 2.
However, the conventional optical inspection system 7 cannot be applied to certain DUTs, such as objects having mirror surfaces. With such objects with mirror surfaces, a large amount of the emitted light cannot be reflected to the camera 72, since this light is reflected from the objects in a manner that follows the law of reflection. Therefore, the intensity of the reflected light received by the camera 72 is too low, so that image contrast is poor, thus affecting subsequent algorithmic interpretations. Even if the optical inspection system 7 can be modified to be in accordance with the law of reflection and thereby obtain better image contrast, problems of shadows and image distortion of the captured images will occur. The problem of image distortion can be compensated for using an algorithm, but the problem of shadows cannot be overcome.
Accordingly, those in the industry are endeavoring to provide an optical inspection system that is able to solve the aforementioned problems.